The present invention concerns a system for the treatment of unsorted waste. The present invention further concerns apparatuses which may be used in such a system.
The unsorted waste dealt with by the present invention includes solid or semi-solid waste produced primarily in households, offices, etc. Such waste, in most cases is composed of solid waste resulting from human consumption. This includes, for example, food scraps, yard waste, organic materials and any other materials of widely varying physical characteristics such as fibrous material, e.g. paper, cardboard and rags, plastic material, glass, wires, light gauge metallic containers, and relatively heavy, materials such as heavy metal pipes and iron castings. Such waste will be retreated to herein as xe2x80x9cmunicipal solid wastexe2x80x9d (MSW).
The treatment and/or disposal of MSW presents a major challenge in the urban setting. It has become particularly problematic in recent years as a result of growing population and an increase of per capita consumption. The treatment and/or disposal presents a continuously growing challenge to urban authorities.
Conventionally MSW has been disposed of by such means as incineration, land fills or recycling. Recycling requires some discipline on behalf of the inhabitants in initially sorting the MSW into its major constituents, e.g. metal, glass, organic waste, etc., and disposing each type of waste in a different container
Burial of MSW or disposal in land fills concentrates the MSW in a single location. Such a waste treatment method has various environmental undesired effects including risk to contamination of ground water, maleodors, attraction of various pests which thrive on the waste, and others.
Incineration presents a major problem of air pollution. In addition, it presents a problem of disposal of the produced ash particularly as it may contain relatively high concentration of non-combustible toxic substances such as toxic metals. The energy required for combustion is primarily used for the initial removal of the liquid from the waste and some separation of the waste to its components.
Recycling of certain waste material is again problematic by current methods, as it requires separation of the material into its components, which as pointed about above, necessitates a measure of discipline from the inhabitant to separate waste material into its component. Experience shows that is never completely satisfactory.
U.S. Pat. No. 1,298,577 discloses a system for separation of gold from sand using a device that allowed heavier gold to settle out of a moving water stream with the sand remaining suspended. U.S. Pat. No. 5,548,971 disclosed the separation of rocks from wood chips by using an apparatus which subjected the mixture of wood chips and foreign particles, such as rocks and nails, to an upward flow of water. The employment of water floatation techniques for the separation of ingredients in MSW include U.S. Pat. No. 3,568,839, U.S. Pat. 3,597,308 U.S. Pat. No. 3,987,215, U.S. Pat. No. 4,250,023 and U.S. Pat. No. 5,387,267. These patents had the objective to yield a complete separation of organic material, including paper, textiles, wood, plastic and food waste from inorganic material such as metals, glass, sand and dirt in order to produce a low ash content fuel or compost material. Nevertheless, none of these patents enable separation of collected, unsorted waste and recycling of the waste components after their being separated.
The present invention provides, by its first aspect, a system for treatment of collected unsorted waste, comprising a waste receiving pit; at least one first separator for separating between first waste material having a specific gravity equal or less than that of water and second waste material having a specific gravity above that of water; at least one crusher for receiving said first waste material, substantially crushing at least a particular portion thereof to a smaller particulate form to obtain treated waste material and producing a liquid product comprising water carrying the treated waste material; at least one acetogenic fermentor for receiving said liquid product and for anaerobic acetogenic fermentation thereof to produce a first fermented effluent; at least one methanogenic fermentor for receiving said first fermented effluent and for anaerobic methanogenic fermentation thereof to produce a second fermented effluent; at least one liquid feed line for feeding at least one of said first or said second effluent into one or more of the system""s devices for subsystems.
The present invention further provides by other of its aspects, an apparatus for separation of collected unsorted waste, and an apparatus for treating a liquid which carries waste particles. These two apparatuses may be used, in the above system, in accordance with some preferred embodiments thereof.
The invention thus provides in accordance with a second aspect thereof, an apparatus for separation of collected unsorted waste, comprising a liquid-holding receptacle with an open top for receiving the waste and a bottom end formed with a sink portion for receiving a first waste material having a specific gravity larger than that of water; a first conveyor with its bottom end within said sink portion and its top end extending out of the receptacle to convey the first waste material from said sink portion to a first collecting device outside said receptacle, and a second conveyor with its bottom end at another portion of the receptacle being at a level higher than that of said sink portion to convey a second waste material having a specific gravity below that of water, to a second collecting device; a barrier-defining member situated above said first conveyor at a clearance therefrom permitting delivery of the said first waste material by said first conveyor and defining a barrier for articles introduced into the receptacle from directly contacting said first conveyor but in said sink portion; liquid injection nozzles disposed within said receptacle for injection of liquid streams into the liquid within the receptacle to impart lateral movement onto articles within said liquid.
According to a preferred embodiment of said second aspect, the apparatus comprises a shredding device for shredding solid matter dispersed with said liquid. The shredding device may have the general form of a rotating cylinder with arcuated blades for cutting or shredding the solid matter as a result of its rotation. This arrangement is particulary important for the purpose of shredding plastic material such as plastic bags, disposable diaphers, which are one of the characteristics and which present a major disposal problem of household waste. The shredding device can also facilitate of closed plastic bags.
The present invention thus provides in accordance with a third aspect thereof, an apparatus for treating a liquid carrying waste material, comprising a tubular body defining of flow path between a liquid inlet and a liquid outlet, the tubular body having a plurality of straight sections, two adjacent sections, consisting of a proximal section being the one more proximal in the flow path to the inlet and a distal section, being connected to one another at ends thereof to form corners with angles between them, at their point of contact; and high pressure liquid nozzles disposed within the tubular body at said corners thereof and arranged such that they inject an axial jet of pressurized liquid into the distal section.
In the current disclosure, above and below, the terms xe2x80x9ccollected wastexe2x80x9d, xe2x80x9cMSWxe2x80x9d, xe2x80x9chousehold-derived wastexe2x80x9d, xe2x80x9cMunicipal unsorted-solid wastexe2x80x9d and other similar terms or derivation thereof, may be used interchangeably. The present invention is useful for the treatment of waste of a variety of different sources. It should be noted that the exact constituent of the MSW may change from one locality to another, depending on whether it is derived from a residential area, from an office area; etc. from one to another; seasonably; independent to the climate, etc. It is a characterizing feature of the invention that initial separation of the waste to its components is not required. Furthermore, in accordance with the invention, the various components are collected separately and may subsequently be recycled.
The system, in accordance with one embodiment thereof comprises a sorter subsystem for receiving said second waste material and for sorting it according to predefined characteristics. This sorter subsystem may employ sorting apparatuses of a kind generally known per se. In accordance with a preferred embodiment, the sorter subsystem is connected to at least one liquid feed lines for rinsing the sorted waste material and thus consequently, a rinsed separated material ready for re-cycling is obtained. Such material may include glass, ferrous and non-ferrous metals. Ferrous metal and non-ferrous metal may be separated from one another based on the magnetic properties of the ferrous metal.
In accordance with one preferred embodiment of the system, the first separator is an apparatus according to the second aspect of the invention.
In the separator, the barrier-defining member according to the second aspect of the invention, is preferably a planar and situated essentially parallel to said conveyor. The nozzles may, in accordance with one embodiment of disposed or formed at the upper wall of said barrier-defining member. The barrier-defining member typically extends between side walls of the receptacle situated opposite one another on both sides of the first conveyor.
Typically, said second waste material is fed first into one or more devices which subjects the waste to an initial treatment by grinding, shredding or both, and only then this treated waste product is fed into the crusher.
In accordance with another preferred embodiment, the system comprises a filtration-separation subsystem for receiving the liquid waste material and separating particulate material therefrom with a particle size above a predefined size. Further in accordance with this preferred embodiment, the system typically comprises a feed line for feeding the separated particulate material back into the crusher with another feed line, for feeding the separated liquid, typically collected in a filtered liquid reservoir to the acetogenic fermentor.
In accordance with one preferred embodiment, the crusher in the system is the hydro-crusher apparatus according to the third aspect of the invention. The nozzles in this hydro crusher are typically connected and receive high liquid pressure from a high pressure pump which pumps liquid from the filtered liquid reservoir which contains a liquid separated by filtration and separation subsystem.
The filtration and separation subsystem, in accordance with this preferred embodiment of the invention, comprises three devices as follows: a first, filtration and separation device, for receiving the liquid product containing the liquid waste, filtering out therefrom particulate material of a size above a predefined size and for separating a sediment-containing fraction from the filtered liquid, to obtain a first filtered liquid; a second, separation device for receiving said sediment-containing fraction, separating between the sediment and the liquid to obtain a second filtered liquid; and a third, filtration device for receiving said first and second filtered liquid, filtering out particulate material therefrom of a size larger of the predefined size, to form a filtered liquid reservoir and a particulate material-containing fraction. In accordance with this embodiment, the system preferably comprises also a feed line for feeding said particulate material-containing fraction back into said crusher.
The tubular body of the apparatus in accordance with the third aspect, typically forms a prismatic-shaped spiral. The spiral is preferably right-angled. The apparatus in accordance with this aspect is typically associated with a first treatment device for a pretreatment of the liquid to grind or shred the particulate material therein; and at times also with a second treatment device which is connected to the outlet of said tubular body for removing articles of defined characteristics from the liquid exiting from said outlet, e.g. the above defined filtration and separation subsystem. The second device, as is clearly elucidated from the description of the system above, is typically connected to the inlet of the apparatus to transfer thereto at least a portion of the separated articles for re-treatment.
Other preferred embodiments of the system will be elucidated from the detailed description of the invention below.
The invention will now be illustrated further in the following description of specific, non-limiting embodiments.